Basically, exactly what it says on the tin. How exactly do you put this undead SOB down? I'm loading up on resistance potions, and I'm using both Spellbreaker and Phantom Form, like the wiki says, but I still can't put him down (at least not before either I die or he heals himself completely). Any suggestions on what I should be doing? I'm playing as a lvl 71 Altmer battlemage (focused on Destruction, Conjuration, Restoration, Archery, Sneak and One-Handed Weapons).

It's intentionally a difficult fight, if you've watched my playthrough of the quest you'll see me die a few times as well.

Keep an eye on the spell he has in his hand; if it's red or white he's probably going to cast a large destruction spell. Use Phantom Form to keep him occupied and snipe him from a distance or stagger him with a shied or weapon to prevent him from casting spells.

From my AI playtesting the first thing he'll do is resurrect a draugr death overlord behind him so before you start the fight, drag that corpse as far away as possible and any others as well. He should rarely head towards the entrance so drag the corpses there.

The second thing he does is cast a blizzard spell then firestorm so try to keep away from him when he's doing that. After he's cast those he'll use lightning wall and chain lightning so take an Elixir of Shock Resistance then attack.

The first time you get his health down to 80% he'll heal completely because of a perk he has. After that he'll use a custom healing spell that'll revive 50% of his health at a time so if you see a yellow spell in his hand, keep staggering him to prevent him from casting it.

Make sure you've tempered your weapons as high as possible and wear as much spell-resistant gear as possible.

Ended up beating him a little while back after getting back into Skyrim. Ended up luring him down the hall a bit with Phantom Form, then dual-casting Wall of Flame and soaking the area until he dropped. More of just a lucky break/cheap tactic than anything, but considering how utterly OP the boss is, I don't particularly give a toss.

He KO'ed me in about 10 seconds...so reloaded, poisoned a cross bow bolt with a 130% drain magicka poison potion, 'cross bow specks-enhanced Dwarven 249pw 30+ burn, soul trap death 17sec, 30+ electrify' bolt was a Dwarven fire bolt and another four shots as well as Sarana blasting him with magic Ice bolts and vampire health drain, oh and I was crouching half way back up the entrance hallway .... Vulom is powerfull and one mean SOB. lol (lvl 49)